Television reception



H. Pv. DONLE 1,903,986

TELEVISION RECEPTION April 1 8, I1933.

Filed sept. 17, 1928 lrdntenteri Apr. 18, 1933 l interet ion HELB il. DDE-XLR, OF mmm, GQBWECTCUT, SSIGJGB T@ MDE@ ETVENTONS, @Gn

y A CQRPOMTEON @E NEW YDBK Application med September 1?, 1928. Seriell Ho. 308,360.

According to general practice the picture is transmitted electrically either by Wire or radio and the transmitting circuit customarily includesla so-called photoelectric cell o which is sensitive to li ht. This cell is subjected to pulsations of ight derived sequentially from small areas of the object Whose picture is'to be transmitted. These pulsations of light are customarily produced by lo means of a disc having spirally arranged openings and rotated at a. predetermined speed. Reproduction of the picture 1s aci complished by apparatus which includes e scanning disc rotated at the speed otthe transmitting disc and having perforations transmitter. y

in the past it lies been found dicult to maintain synchronism between the scanning c disc or the reproducer or receiver end the scanning disc oi' the transmitter.

The main object of my present invention is tc .automatically synchronize the reproducer the 'transmitter Without requiring addifticnnl circuits or mechanical devices. To acccinpiish this with a maximum degree ci siro plicity and certainty il synchronize receiving up; arutus *with the electrical impulses correspon `ing with the light impulses of the picture which is being received.

lin the simplest forni ci apparstus ier cer rying out any invention l provide a synchronizing regulator Whose armature is connted with the scanning disc oi the reproducen This armature is provided with e series ci pole pieces ccrrespondine 'with the perorations in the scanning disc. The held coils et the regulator are connected in circuit 'efith the lamp Whose light furnishes the picture.

Fig. i is an edge view ci the scanning disc and its regulator embodying" my invention.

Fig. 2 is a diagram oi3 e circuit ci apparatus embodying; my invention.,

Fig. 3 is e rece view ci the preferred form ci scanning disc. v

Fig. 4i is a ieee View or a fragment of the armature. v

Fig. 5 is a :tace view ci e fragment ci the eld coils ci the regulator.

which synchronize with perforations ci the tating.

The motor may be of any suitable type and is designed so that it would normally tend to rotate at or near the speed of the transmitting disc.

flhe scanning member or disc 1l is of any suitable character preferably very thin and light in Weight so thatv it will have a minimum inertia. rlhis disc preferably has a ser1es of perforations such as 12 arranged in tivo spirals as shown in Fig. 3 so that tivo pictures may be seen at all times. By locating the observation point properly one of these pictures may be selected or observed. This' disc is mounted in a suitable manner on the shaft 13 and driven by the The motor shaft also carries an armature disc lli having a series of redini bars l con 3" responding in number with the perfor ions in the scanning disc. This ermature p cierabiy et iron., oi? high pernosability",i for inu stance9 of siiicon steel, The field. coils it ci the regulator' are supported on the plete l?" which in turn is supported in a suitable man ner from the motor casing or trame. These coils i6 are spaced apart circumerentially to correspond with the bars 15 above described. There may be a coil for each bar or 85 one coil ior every second,l third, or fourthhar. The exact number oi coils is not vital but the apparatus is more sensitive with a large number of coils. V

l'n Fig. 2 as illustrated the field coils ci the re `alator are connected in a typical circuit including the tubeof the last stage oi audio i'requency amplicatiomthe lamp 2l for instance bein a neon lamp, and an amplifier tube 22 which is preferably interposed be tween the lame and the regulator.

The fluctuations in the current through the lamp 2l occur somewhat as illustrated in Fig. 6. The zero or minimum current interval at 23, 24, 25, etc. correspond with the interval nals are, of course, transmit while the perforatlons are in line or registry with the transmitting light source or optical image, and the synchronizing signal is transmitted during the interval between two successive picture signals. series with the neon lamp 1s a small resistance 26 across the terminals of which is connected the-amplifier tube 22, the plate circuit of which is connected to the field coils. The amplifier tube 22 is connected across this resistance in such a way that when current is flowing through the neon lam the grid of the amplifier tube 22 is charge negatively thus allowin only a small plate current to ilow throng when the current through the neon lamp 21 v is reduced to or near to zero atthe points 23,

24, 25, etc. this negative charge on the grid of the ampliiier 22 is removed and a large current iiow's through the plate circuit and the field coils thus ener izing the latter. The current fiowing throng the late circuit of the amplifier` and through t e field coils is shown 1n Fig. 'I where a large pulsation of current takes place at the intervals 27, 28, and 29 corresponding to the no-current points 23 24, and 25 respectively above described..

z[he result of this arrangement is that when the reproducing disc 11 is rotating in exact synchronism with the transmitting disc the maximum impulse points 27, 28, etc. occur when the poles of the coils are opposite the bars 15 of the armature disc.

In case the speed of the transmitting disc increases or decreases the maximum current impulses in the lamp 21 will occur earlier or later as the case may be thus producing a retarding or accelerating relation between the stationary field coils and the bars or arms 15 of the rotating armatureattached to the reproducing disc 11. This in eect locks the disc 11 in exact chronism with the transmittin disc w `ch will be maintained throng out' a wide vam'aticn in speed of the transmitter disc due to the locking action of 'this device.

I claim:

1. In television receiving apparatus, a sysc tem for synchronizing the speed of a rotating armature with received signals, including a circuit having an element that passes substantially no current for less than a minimum applied voltage, means for impressing varying currents u n said` circuit, means -for periodically ucing the voltage applied to said element below said minimum, a resistor 55 in said circuit Iand means for applying a the amplifier, but

drop of potential developed across said resistor to the input of a vacuum tube relay whereby for minimum current in said circult maximum current is delivered by said tube, a magnetic system acting upon said armature, and means for applying said tube current to said system. 1

2.- Television receiving and synchronizing circuits including a light producing element -having a sharp lncrease of resistance when less than a definite potential is applied thereto, a resistor connected in series with said element, and a vacuum tube having its input circuit connected-to said resistor, the clarity of such connection being such that w1th normal current owing through said first named circuit the input electrode of said tube -is suiciently negative to prevent substantial current from flowing in the output circuit of said tube.

3. In a television system an input circuit carrying picture and synchronizing signals, an output circuit coup ed to said input circuit, and including an electro-optical translating device subject to said signals, said output circuit also including a |coupling member,

a phase inverting relay having its input circuit so connected 'to said coupling member that the bias produced b the picture si al alone causes the relay to me non-con uctive, while the bias produced by the synchronizing signal allows the' relay to become conductive, said relay having an output circuit including scannin control means actuated by the synchronizing signals in the output i clrcuit.

4. The method of operating a television system which comprises generating picture and synchronizing signals, amplifying said signals, passing said signals through a series circuit contalning an electro-optical device and a. coupling member, causing the voltage generated by the picture signal alone in sald coupling member to bias a phase inverting synchronizing relay to an inoperative condition, and causing the said relay to become operative by the voltage generated by the synchronizing'v signals.

HAROLD P. DONLE.

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